Add user theme support and migrate frontend to HTMX templates

- Add theme column to users table with default 'tokyo-night'
- Update all user queries to include theme field
- Add ListUsers and UpdateUserTheme database queries
- Update auth handlers to support HTMX form submissions and JSON API
- Add ListUsers API endpoint
- Replace embedded static files with Go templates
- Update Dockerfile to copy templates directory
- Redesign index.html with inline styles and HTMX forms
- Update Bruno API testing requests for auth endpoints

bruno/auth/List Users.bru

@@ -0,0 +1,40 @@
+meta {
+  name: List Users
+  type: http
+  seq: 5
+}
+
+get {
+  url: {{base_url}}/api/users
+  body: none
+  auth: inherit
+}
+
+settings {
+  encodeUrl: true
+  timeout: 0
+}
+
+docs {
+  ## List Users
+  
+  Retrieves a list of all users.
+  
+  **Method:** GET
+  
+  **Endpoint:** /api/users
+  
+  **Authentication:** Required
+  
+  **Response:** Array of user objects
+  - `id` (string): User ID
+  - `email` (string): Email
+  - `username` (string): Username
+  - `theme` (string): User theme preference
+  - `created_at` (string): Creation timestamp
+  - `updated_at` (string): Last update timestamp
+  
+  **Status Codes:**
+  - 200: Success
+  - 401: Unauthorized
+}

bruno/auth/Login User.bru

@@ -20,7 +20,7 @@ body:json {
 script:post-response {
   function onResponse(res) {
     let data = res.getBody();
-    let token = bru.setEnvVar("token", data.token, { persist: true });
+    return bru.setEnvVar("token", data.token, { persist: true });
   }
   onResponse(res);
 }

bruno/auth/Register User.bru

@@ -18,32 +18,33 @@ body:json {
       }
 }
 
+script:post-response {
+  function onResponse(res) {
+    let data = res.getBody();
+    return bru.setEnvVar("token", data.token, { persist: true });
+  }
+  onResponse(res);
+}
+
 settings {
   encodeUrl: true
   timeout: 0
 }
 
-script:post-response {
-  const data = res.getBody();
-  if (res.getStatusCode() === 201) {
-    bru.setEnvVar("token", data.token);
-  }
-}
-
 docs {
   ## Register User
-
+  
   Creates a new user account.
-
+  
   **Method:** POST
-
+  
   **Endpoint:** /api/auth/register
-
+  
   **Request Body:**
   - `email` (string): Email address
   - `username` (string): Username
   - `password` (string): Password
-
+  
   **Response:**
   - `token` (string): JWT token
   - `user` (object): User details
@@ -51,7 +52,7 @@ docs {
     - `email` (string): Email
     - `username` (string): Username
     - `theme` (string): User theme preference
-
+  
   **Status Codes:**
   - 201: Created
   - 409: User exists